Electrical utility service providers, or simply utilities, monitor energy usage by customers through electrical utility meters. Electrical utility meters track the amount of energy consumed, typically measured in kilowatt-hours ("kwh"), at each customer's facility. To this end, one or more electrical utility meters are connected to the power lines of a facility through a meter socket or similar arrangement. Utilities use the metergenerated consumption information primarily for billing, but also for resource allocation and other purposes.
Utilities generate polyphase electrical power, and typically, three phase power. Polyphase electrical power is alternating current electrical power that is supplied on a plurality of power supply lines, wherein the voltage waveform on each of the power supply lines has a unique phase angle with respect to others. Single family dwellings typically only use a single phase of the polyphase electrical power generated by the utility. By contrast, industrial, commercial, and multiple family dwellings generally use multiple phases.
Historically, electrical utility meters utilized an inductive spinning disk mechanism to measure energy consumption. In such meters, the rate at which the spinning disk rotated would vary proportionately to the amount of power being consumed. The spinning disk then drove mechanical counters that accumulated the energy consumption information.
A recent development in electrical utility meters are electronic meters. Electronic meter replace the older inductive or spinning disk meter design. Electronic meters rely on the digital sampling of the voltage and current waveforms on the power lines to generate energy consumption data. Electronic meters have several advantages, including the advantage of providing features beyond straightforward power consumption metering. For example, electronic meters may track energy demand, power factor, and per-phase power measurements. In addition, electronic meters may alter the method in which they calculate energy consumption in order to accommodate several building wiring and power configurations, thereby increasing the versatility of a single meter design.
A problem associated with electrical utility meters is inaccurate energy consumption measurements caused by improper installation or tampering. For example, improper installation can include situations in which the power lines are improperly wired to the meter socket. Improper wiring generally results in the meter measuring an inaccurate amount of energy consumption. However, such improper installation does not affect power service to the customer, and therefore goes unreported. Accordingly, the improper wiring error and resultant energy consumption measurement errors can go undetected for years. The inaccurate energy consumption measurements caused by the improper installation can result in large revenue loss for the utility.
Electronic meters have addressed this problem by incorporating fairly sophisticated diagnostics that detect measurement errors caused by improper installation and some forms of tampering. For example, U.S. Pat. No. 5,469,049 to Briese et al. shows a diagnostic toolbox that is built into a meter. The diagnostic toolbox in the Briese et al. device measures per phase voltage and current magnitude and phase angles. The measured voltage and current magnitude and phase angle values are compared to expected values to determine if one or more measurement errors are indicated.
According to Briese et al., certain codes are displayed on the meter display if an error is detected. The displayed code contains an identification of the error detected. The device disclosed in Briese et al. further displays the current and voltage magnitude and phase angle values upon request. Accordingly, the diagnostics of the Briese et al. meter provide for some detection of measurement errors that may result in loss of utility revenue.
A shortcoming of the device disclosed in Briese et al. is that it requires the physical presence of a utility field technician to obtain the error information. Specifically, the error information generated by the diagnostic toolbox is displayed on the meter display. Accordingly, it a customer or another party that is not related to the utility introduces a change in the wiring of the meter, then even if the meter detects the error, the utility will not be notified of the error until a utility field technician travels to and reads the meter.
For example, a party may tamper with the meter by rewiring the power line phases, thereby reducing the measured energy consumption. The utility may not visit the site for an extended period and therefore may not learn of the error, even thought the meter may display the error constantly. As a result, the utility may record and bill inaccurate energy consumption measurements for several months until a utility technician visits the site.
Accordingly there is a need for an electrical utility meter having an improved diagnostic capability that reduces the quantity of inaccurate measurements caused by improper wiring and tampering.